Tuesday, 15 February 2011

Cognition researchers should beware assuming that people's mental faculties have finished maturing when they reach adulthood. So say Laura Germine and colleagues, whose new study shows that face learning ability continues to improve until people reach their early thirties.

Although vocabulary and other forms of acquired knowledge grow throughout the life course, it's generally accepted that the speed and efficiency of the cognitive faculties peaks in the early twenties before starting a steady decline. This study challenges that assumption.

A massive sample of 44,000 people, aged between ten and seventy, completed an online face learning test in which they were required to study briefly several unfamiliar faces, presented in grey scale without hair or other non-facial distinguishing features. They then had to identify those faces, shown in novel poses and varied lighting conditions, from among further unfamiliar faces.

As you might expect, performance at the task increased steadily through adolescence. But although improvement slowed once adulthood was reached, it didn't stop there. Performance in fact peaked among those participants aged 31.4 years, after which it declined slowly. The pattern of results meant that average performance by 16-year-olds matched the average performance of those aged 65.

The results suggest strongly that face learning capabilities continue to develop into the early thirties, but an alternative explanation is that the sustained changes are more generic, to do with general memory or cognitive abilities. To rule this out, a second study tested nearly 15,000 people on a face task and also a memory task involving names. As before, face learning ability peaked in the early thirties. In contrast, performance at the learning of names peaked at age 23.

A final study used children's faces, in case the earlier studies' use of more mature faces had given older participants an unfair advantage. Even with children's faces, facial learning peaked in the early thirties. However, this prolonged developmental trend wasn't found for inverted faces (performance with these peaked at age 23.5 years), thus suggesting it's specifically the ability to learn new up-right faces that continues to improve into the thirties. It remains to be seen whether this improvement reflects a kind of prolonged innate maturation process or if it's simply a consequence of more years practice at learning faces.

How big were the increases in face learning performance between the end of adolescence and the early thirties? They were modest (the effect size was d=.021) so more research is needed to find out what real life implications, if any, these lingering improvements in ability might have. Another study limitation is the use of a cross-sectional sample. Future research should study changes in ability in the same individuals over time. Notwithstanding these points, the researchers said 'our data illustrate that meaningful changes can and do occur during early and middle adulthood and suggest a need for integration of research in cognitive development and aging.'
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